Wednesday, January 15, 2014

and says his explanation that there would be no hydrogen explosion is technically correct.

(Continued from Part 1 and Part 2, from Nikkei Shinbun: Testimony of Dr. Madarame, in the third year of the accident: "Worst case scenario was possible for Fukushima" by Junichi Taki, editorial board member)

――事態が当初の見込みよりはるかに深刻だと気づいたのはいつごろか。

--When did you realize that the situation was much graver than the initial assessment?

"I knew something was wrong when I was told that the pressure of the Reactor 1 Containment Vessel was rising, past midnight [of March 11, 2011]. Maybe the DC power stopped, I thought. Still, Reactor 1 could be cooled by the isolation condenser (IC) even in the loss of power situation. Later, I heard the cables from the power supply cars couldn't be connected, or that they needed more cables than available; I speculated that the switchboard was under water, and they were trying to supply power to individual pumps. We (at the Prime Minister's Official Residence) were not aware of what was going on at the plant and what they were trying to do. Human psychology goes from extreme to extreme. I started to feel extremely desperate."

■「安心したことが間違いだった」

"It was a mistake [PM Kan] to feel relieved"

――前夜に進言したベントは明け方になっても実行されていなかった。

--The vent you suggested the night before wasn't carried out by the next morning.

"The purpose of the vent had vastly changed from the previous night. By that time [morning of March 12, 2011], it could be assumed [I assumed] that the reactor core melted, and the pressure inside the Containment Vessel was rising (because of water vapor and gas). The vent was necessary in order to protect the Containment Vessel (from damage)."

――早朝になって、避難指示の区域を10キロ圏に広げている。

--In the early morning [of March 12, 2011] you expanded the evacuation zone to areas within 10-kilometer radius.

「炉心が溶けているとすると、３キロでは足りないと思った」

"I thought 3-kilometer radius was not enough if the reactor core melted."

--If your assessment of the situation was that pessimistic, why did you accompany (then) Prime Minister Naoto Kan in the early morning on a helicopter and told him "there would be no hydrogen explosion"?

"Prime Minister asked me what would happen if the reactor core was exposed. I answered hydrogen would be generated. He then asked me if that would lead to an explosion. So I answered there would be no explosion because the Containment Vessel was filled with nitrogen (and there was no oxygen). My explanation is not wrong. Former Prime Minister Kan writes in his book that it was a "big mistake" to feel relieved by my words, but my explanation is not wrong. It was a mistake (for Prime Minister Kan) to feel relieved."

「ヘリに乗る直前に、これからベントを行うとの連絡を聞いていたように思う。現地に着くまでにベントは実施されるものだと思っていた」

"I think I heard, right before we boarded the helicopter, that they were about to do the vent. So I thought the vent would have been done by the time we arrive at the plant."

――とすると、ベント直後の発電所に降り立つことになるが、ヘリに乗った人たちは防護服を着ていなかった。

--If what you say is true, then you would have landed on the plant right after the vent. But no one on board the helicopter was wearing the protective clothing."

--It is said that Prime Minister Kan, on getting off the helicopter, shouted at (then) TEPCO Vice President Sakae Muto, "Why aren't you doing the vent?" So the prime minister knew that the vent hadn't been done.

"I didn't hear the conversation between the prime minister and Mr. Muto, but I suppose the prime minister must have been told about (the vent not being done yet). I was told in the conference room of the Anti-Seismic Building [at the plant]. The prime minister may have used strong words about the vent because I emphasized to him the importance of the vent when we were on board.

0:55AM Pressure inside the Containment Vessel of Reactor 1 rising; power supply cars arrived, but the power couldn't be restored; [Madarame] suspected the damage of the power control panel
3:00AM confirmed operation of Reactor 2 reactor core isolation cooling (RCIC), decided it was Reactor 1 that was in danger
5:00AM asked to accompany Prime Minister on the on-site inspection
5:44AM evacuation instruction to 10-kilometer radius areas
6:14AM leaving PM Official Residence on a helicopter with PM Kan, explaining about hydrogen explosion to Kan on board the helicopter
7:11AM arrived at Fukushima I NPP, learned that vent hadn't been done
8:04AM left Fukushima I NPP
10:47PM arrived back at PM Official Residence, and walked back to the office of Nuclear Safety Commission
12:08PM Nuclear Emergency Response Headquarters meeting (Madarame was asked at 11:35AM to attend)
1:00PM met with Members of the National Diet elected from Fukushima (stayed in the prime minister's reception room from 1:30PM on)
3:18PM news of successful vent of Reactor 1, discussion of issues concerning seawater injection [into the reactors]
3:50PM news of white smoke rising from Reactor 1

In other words, the vent may have caused the explosion after all (that was the conclusion of none other than NISA in December 2011). If the vent had been successfully carried out by the time Mr. Kan and Dr. Madarame arrived at the plant, they may have been just in time to witness the Reactor 1 explosion firsthand.

15
comments:

Anonymous
said...

@Laprimavera. A vent cannot cause itself such an explosion, as 1) it goes out through a well-separated exhaust stack, and 2) the hot hydrogen-containing gases are much lighter than air.The fact an explosion happened means there was a leak into the building, from the vent pipes and/or the containment itself, caused by excessive pressure or temperature, or even by quake damage. Is the cause now known?It is mind-blowing there were no automatic safeguards against containment overpressure (rupture disks), which are standard fare in most European plants. And the vents are filtered, too…

The exhaust stack wasn't well-separated, and hydrogen leaked back into the building through the standby gas treatment system. Or so NISA and TEPCO think. http://ex-skf.blogspot.com/2011/12/now-they-tell-us-series-nisa-says.html

Thanks for the link. However, as one of the commenters pointed out, the link between the building and the exhaust stack is not just a "standard" ventilation exhaust, but will be a small-flow filtered one, to trap small emissions of noble radioactive gases (Kr, Xe):http://files.asme.org/Divisions/NED/31871.pdfThis is not directly linked to the atmosphere inside the building, but, through piping, to reactor auxiliaries.The building itself would IMHO only require venting to the atmosphere, as it should normally contain only very little radioactive gases.So either this is a serious design flaw, or another additional problem was involved, which TEPCO/NISA didn't identify - or identified, but did not make public…

Whether the exhaust stack was connect directly to containment is a mute point. Station blackout turned into intermittent battery supplied power. Valves were nonoperational unless manually manipulated. Sure there were auto venting valves but not large enough to handle a full blown meltdown. The major design fault of a Mark I. The containments (reactor and primary) began self venting through o-rings [the lid to vessels seals (and probably elsewhere)]. A primary lid seal leak vents onto floor 5 like you see still happening Unit 3 occasionally.

Unit 2 building was saved by losing a side panel thus vented the building to open air but it still melted down and out. If chopping holes in Units 5&6 roofs was precautionary or not, TEPCO learned their lesson to late to save Unit 1,3&4 buildings.

A makeshift fix for the undersized Mark I containment is adding harden pipe to vent primary containment directly out the side of the building (shortest possible route). Here in the US, NRC waffles on requiring them because plant operators claim costs are prohibitive. Or, they already can't compete with conventional power plants and further major modifications will put them out of business. Safety is secondary.

@2:42: Your hypothesis of "self-venting" due to overpressure and excessive temperature seems quite plausible to me.The NRC's decision is incomprehensible, given the fact that 1) such changes have been done in Europe at relatively low cost 20 years ago, and 2) their own staff came out in favour of this option!http://www.nrc.gov/reading-rm/doc-collections/commission/secys/2012/2012-0157scy.pdf"…the staff concludes that installation of engineered filtered venting systems for Mark I and Mark II containments is the option that would provide the most regulatory certainty and the timeliest implementation. The vast majority of Mark I and Mark II severe accident sequences would benefit from a containment vent, (whether the vent includes an engineered filter or not) and the addition of an engineered filter reduces the release of radioactive materials should a severe accident occur. A comparison of only the quantifiable costs and benefits of the proposed modifications, if considered safety enhancements, would not, by themselves, demonstrate that the benefits exceed the associated costs. However, when qualitative factors such as the importance of containment systems within the NRC’s defense-in- depth philosophy are considered, as is consistent with Commission direction, a decision to require the installation of engineered filtered vent systems is justified."At least, the NRC is much more transparent than the Japanese: the staff report is public, and the commissioners won't be able to escape responsibility in case of an accident by pretending they didn't know!

11:51,you are not trying to make readers believe that *all* European npps have filtered vents, right? I know that, technically, "standard" (?) is not a synonym of "all" nor a synonym of "most", but just to be clear.

I also suggest to replace the term "containment" with the more descriptive "colander". This simple operation will allow nuclear industry to shed further responsibility in case of a severe accident: no one will be able to claim he did not know the dangers involved in nuclear generation.

I believe Kan did not make a mistake by feeling relieved at Madarame assurance that there would be no explosion.Madarame is talking like a lawyer when he says he was technically correct; his duty was to make sure Kan understood the situation and he failed at that.Furthermore, in this third installment Madarame is again "supposing" way too often (and incorrectly). He should have got his back on a helicopter and started reporting to Kan from Fuku 1.Beppe

To readers just browsing, 'venting' whenever used in conjunction with a nuclear plant means the reactor is being relieved of a pressure buildup for whatever reason but the actual venting is a radioactive release. Not ever a good thing. Some plants have tall stacks to release radioactive steam/gases/particles high into the air, that is only to get the radioactivity away from the plant site and allow workers less exposure to radioactivity.

Claims that controlled venting is filtered and radioactivity is captured before release is not entirely true. You can't filter and capture everything.

During a core meltdown, without a way to cool it as at Fukushima, Daiichi, you can only standby and watch as containment is ruined and radioactivity blows out uncontrollably like an overheating teapot full of explosive hydrogen gas and radioactive materials.

@12:00: Venting is of course never a good thing, as it usually means hydrogen is being evolved (= degradation of fuel cladding = core damage).While you certainly can't filter noble gases in an emergency vent, these aren't that bad (they dissipate and won't contaminate the land). What you can filter is >99% of iodine (the worst short-term stuff, = thyroid cancer), and >99.9% of caesium (the long-term radiation and evacuation). Strontium will be filtered as well, but is not much there anyway (not so volatile).What happens with a full core melt depends on the plant and severity of the accident, but it seems the core didn't go through the concrete basemat at Daiichi. Many newer designs even take this into account, and have a so-called "core catcher" (e.g. VVER and EPR series, now required by many regulators).There's no denying a core melt is anyway a huge mess, but keeping the consequences confined to the plant makes it much more tractable…

Daiichi with its Mark I flawed containments designed in the 50's- 60's, didn't catch or contain any of the 3 blown reactor melts. Unless you consider the Pacific Ocean part of containment or human lungs as filters.

What does the US have? About 30 Mark I type containments still operating today on extended life timelines? 80+ worldwide?

'The Long Tragic Trail of Defective General Electric Nuclear Reactors, from Hanford to Fukushima'"...When GE first introduced its nuclear power plant technology to the world in the 1950s and 60s, GE’s own engineers and management knew the containment design was deeply flawed and in need of testing and upgrades, according to memos introduced in lawsuits against GE that were filed by several American utilities that bought the reactors...."http://times.org/2013/12/18/the-long-tragic-trail/

About my coverage of Japan Earthquake of March 11

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